Hi all,

I have a couple of problems I am stuck on. I'm never been great with limits, so trying to learn them in 3 and 4 dimensions is a challenge:

Find the limit (or prove that it does not exist) for the following:

lim (x,y)-->(0,0) of xy^4/(x^2+y^8)

lim (x,y,z)-->(0,0,0) of (xy+yz+zx)/(x^2+y^2+z^2)

Thanks in advance!